// https://www.cnblogs.com/lhb25/p/loading-spinners-animated-with-css3.html
.spinner {
    width: 20px;
    height: 20px;
    margin: 5px auto;
    background-color: #37C700;
    border-radius: 100%;
    -webkit-animation: scaleout .5s infinite ease-in;
    animation: scaleout .5s infinite ease-in;
}

@-webkit-keyframes scaleout {
    0% {
        -webkit-transform: scale(0.0)
    }

    100% {
        -webkit-transform: scale(1.0);
        opacity: 0;
    }
}

@keyframes scaleout {
    0% {
        transform: scale(0.0);
        -webkit-transform: scale(0.0);
    }

    100% {
        transform: scale(1.0);
        -webkit-transform: scale(1.0);
        opacity: 0;
    }
}